A good method of discovery is to imagine certain members of a system removed and then see how what is left would behave: for example, where would we be if iron were absent from the world: this is an old example.

It often takes more courage to change one's opinion than to stick to it.

He who is in love with himself has at least this advantage - he won't encounter many rivals.

Man loves company - even if it is only that of a small burning candle.

There is a great difference between believing in something and believing in it again.

I cannot say whether things will get better if we change; what I can say is they must change if they are to get better.

It is in the gift for employing all the vicissitudes of life to one's own advantage and to that of one's craft that a large part of genius consists.